Light polarizing headlight lamination



Nov. 9, 1948. H.' o. BuzzELL LIGHT POLARIZING HEADLIGHT LAMINATION Filed umn 7,- 1946 Patented Nov. 9, 1948 OFFICEA LAMINATION Harold 0. Buzzell, Wollaston, Mass., assignor to Polaroid Corporation, Cambridge, Mass., a corporation of Delaware Application March 7, 1,946, serial No. 652,654 3 claims. (ci. 24o-9.5)

This'invention relates to light-polarizing headlights for automotive vehicles and the like.

It is an object of the invention to provide a light-polarizing headlight of the so-called sealedbeam" type having a substantially flat, multilayer lamination of light-polarizing material and suitable protective l'ayers bonded to its outer lightemitting face.

It is a further object of the invention to provide, in a headlight of the character described, an adhesive layer between the light-polarizing lamination and the outer surface of the headlight lens of such a character as to reduce to a minimum the formation of bubbles within that portion of the adhesive forming the bond which is subjected to maximum heat fromthe filament of the headlightl in use.

A further object of the invention is to form a light-polarizing lamination on the outer surface of headlight lenses of such character as to cushion the various elements against injury due to shocks and blows usuch as may be experienced during usual use.

Accordingly, it is a specic object of the in- I vention to providein a polarizing headlight of the The invention accordingly comprises the article possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the applicationof which will be indicated in the claims.

For a fuller understanding o f the nature and objects of theinvention, reference should be had to the following detailed description, taken in connection with the accompanying drawing, wherein:

Figure 1 represents, somewhat diagrammatically and with element sizes distorted, a vertical section of a headlight of the character described, having bonded thereto a lamination of lightpolarizing material and is illustrative of one embodiment of the invention;

Fig. 2 is a similar view of a modification of the invention; and I Fig. 3 is a similar view of a still further modlflcation of the invention.

The so-called sealed-beam" headlight has been widely adopted as standard equipment for automotive vehicles. It comprises a filament I2 of any suitable type suitably positioned within a reflector I4, which is hermetically sealed to a glass lens element i5 provided on its inner surface with suitable lenticles I6. Headlights of this type as rst produced embodied a convex, spherically curved lens element which created substantial problems in connection with the application to the outer surface thereoi' of light-polarizing material. It was, for example, extremely diillcult, if not impossible, to satisfactorily bond to the spherical surface of.such headlights a preformed sheet of light-polarizing material of any of the types commercially available at the time the headlights were introduced in the market. It has recently been suggested that the shape of the sealed-beam headlight be modied so that the outer surface of the lens element I5 thereof is substantially flat and planar. This invention is concerned primarily with the solution of problems arising from the bonding to the outer surface of the lens element of the new, modified form of sealed-beam heady.

je'cted to treatment .converting certain of its molecules, for example by dehydration, into moleculesv of a light-polarizing substance which has become knownJ as polyvinylene.

In the drawings, wherein like elements are similarly numbered throughout, 20 illustrates the light-polarizing sheetor film. This sheet is preferably bonded to an outer, rigid, impact-resistant,

light-transmitting layer, for example, of glass or some suitable hard, polymerized resin 22, by means of asuitabie adhesive I8, for exam-ple an incomplete polyvinyl acetal such as vpolyvinyl butyral. Under certain circumstances the outer abrasionreslstant layer 22 mayl be scored, for example by ilne, radially-extending score'lines, not shown, to

prevent the setting up of photo-elastic strain patterns therein when the headlight is in use. Where the outer layer is so scored it may be desirable to provide a rigid, transparent supporting layer inat 23, and the polarizing film may be bonded thereto by a second layer of adhesive Ill similar to` that bonding the polarizing layer to the outer 1 The intermediate rigid support 23 may comprise glass of any suitable hard, substantially rigid, light-transmitting abrasion-resistant element.

` prising, in addition to the three elements mentioned, the rigid, inner, supporting layer 22 and the adhesive layer intermediatesaid layer and the polarizing layer, is bonded to'the outer surface of the lens element II, the bond should be accomplished by an adhesive layer 24 which is appreciably thicker in its central portion' than' adjacent its edge portion. This may be accomplished, as shown in Fig". 1, by making the outer surface of the lens element Il of the headlight appreciably concave, or, as shown in Fig. 2, by making the outer surface of the inner supporting element 28 of the polarizing lamination appreciably concave, or'as shown in Fig. 3 by making the adjacent surfaces of the lens element I and the supporting element23 each` appreciably concave.

With anyof the structures shown. there is provided a headlight having bonded to its outer surface a light-polarizing lamination, the adhesive layer between the headlight lens and the polarizing lamination being appreciably thicker adjacent the central portion thereof than adjacent theedge portion. A suitable' adhesive for use in effecting the bond between the polarizing lamination and the outer surfacef the glass lens element i5 may comprise one or more acrylic or methacrylic compounds such, for example,tas a copolymer of butyl methacrylate and methacrylic acid in proportions of approximately 95 parts of the former to 5 parts of the latter. Such an adhesive may be applied between the surfaces to'be bonded together in partially polymerized form and the polymerization of the adhesive layer may then be carried forward to substantial completion by heat.l Another adhesive that has been found to serve admirably, is a mixtur'of 200 parte vby weight of castor oil, and 80 parts by weight of polyvinyl butyral. r

The structures shown in the drawing as providing adhesive layers, between the polarizing lamination and the outer surface of the glass lens of the headlight, of greater thickness in their central portions, are advantageous in that they reduce to a minimum the tendency of bubbles' .to form in the adhesive layer during operation of the headlight by reason of the heat emitted from the filament .vof the lamp which is most intense over the central area of the lens surface. vA relatively thick adhesive layer over this central area has been found to result in the formation of few, if any, bubbles and such a result is. of course, vto be desired as the formation of bubbles alters the eiiect of the lenticles I4. A suitable thickness for the adhesive layer 24 to accomplish the objects of the invention in structures, s uch as are shown in the drawing, is 'approximately 0.001 to 0.010 inch adjacent its edge portion and approximately 0.025 to v0.050 inch thicker adjacent its central portion. v

assai A further distinct advantage to the thicker centered layer 24 of adhesive, is its desirable layer 24 is th'usa`most desirable feature in furthering the useful life and the emciency of the thus equipped headlight.

Since certain'modiileations in the article which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description, or

shown in the accompanying drawing, shall be in'-` terpreted as illustrative and not ina limiting sense. What is claimed is:

1. In a light-polarizing automobile headlight wherein a substantially fiat, planar lamination of 25 a light-polarizing sheet to an abrasive-resistant cover plate is bonded tothe outer surface of a respect to a filament light source as to subject the adhesive comprising said bond to relatively intense heat when the illament'is energized, an adhesive layer bonding the inner surface of said lamination to the outer surface of said lens. at least one of said surfaces being continuously concave, said adhesive layer being appreciably thicker throughout that portion thereof which overlies the central portion of the lens element than por-'- tions adjacent the periphery thereof.

2. The improvement set forth in the preceding claim wherein the outer surface of the substan- 40 tially flat lens element is concave.

3. The improvement set forth in claim 1 wherein the central portion of said adhesive layer is at .least twice as thick as the peripheral portion thereof.

HAROLD O. BUZZELL.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name v Date 1,692,619 Brown Nov. 20, 1928 55 2,092,799 Tillyer Sept. 14, l193'! 2,168,221 Land Aug. l, 1939 2,180,114- Land Nov. 14, 1939 2,237,565 Land Apr. 8, 1941 2,244,702 Hubbuch June 10, 1941 o 2,252,324 Land Aug. 12, 1941 2,320,375 Moulton June 1, 1943l 2,356,250 Land Aug. 22, 1944 2,370,697 Tillyer Mar. 6, 1945 66 FOREIGN PATENTS Number Country Date 460,666 Great Britain Jan. 28, 1937 Great Britain Aug. 28, 1941 substantially dat lens element so positioned with 

